BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 19, pp. 177-192, PLS. 12-13 JULY 23, 1908 



TOPAZ-BEAEING EHYOLITE OF THE THOMAS RANGE, 



UTAH^ 



BY HORACE B. PATTON 



{Read before the Society December 31, 1907) 



CONTENTS 



Page 



lutroductory 177 



Location 178 



Description of Topaz mountain 179 



The topaz-bearing rhyolite 180 



Weathering featiires 182 



Minerals occurring in the cavities of the rhyolite 183 



General reference to the minerals 183 



Topaz 183 



Physical characteristics » 183 



Transparent topaz 184 



Rough opaque topaz 185 



Smooth opaque topaz 186 



Distribution and frequency of the topaz crystals 189 



Specular hematite 189 



Garnet 190 



Bixbyite 191 



Conclusion 191 



Introductory 



For the past twenty or twenty-five years the colorless transparent topaz 

 crystals from the Thomas range of Utah, with their many crystal faccj 

 and wonderfully brilliant luster, have been very familiar objects with all 

 mineral collectors. Although this interesting occurrence has been briefly 

 described by several writers and the crystals have been accurately meas- 

 ured and figured,^ but little information of a detailed nature has been 



1 Manuscript received by the Secretary of the Society March 17, 1908. 

 - Ailing : "On the topaz from the Thomas range, Utah." American Journal of Sci- 

 ence, vol. 33, 1887, p. 146. 



XVIII— Bull. Geol. Soc Am., Vol, 19, 1007 (177) 



